(a) Field of the Invention 
The present invention is related to a 3-action lock barrel, and more particularly, to one that is adaptable to various types of burglarproof lockset. 
(b) Description of the Prior Art 
The prior art of the lock barrel for a burglarproof lockset is generally comprised of a rotor, a case, a row or multiple rows of locking pins and spring. Wherein, the rotor is inserted into the case, one row or multiple rows of radial through holes is provided respectively to the rotor and the case for the upper and the lower locking pins to be respectively inserted into each through hole; and a compression spring is provided at the top of the upper locking pin, All the upper and the lower locking pins are restricted at where between the rotor and the case to prevent the barrel from being turned around. To unlock, a key is required to insert into a keyhole of the rotor to push those lower and upper locking pins to slide until the contact surface of those upper and lower locking pins merely falls on the joint where the barrel is engaged to the case to make possible the rotor to be turned around to open up the lockset. However, those upper and lower locking pins for being held by respective springs are exposed in the keyhole of the rotor. That is, the location of each exposed locking pin can be seen. Anyone attempting unauthorized entry may use  a probe to insert it into the keyhole to press locking pins one by one (by exercising lateral force) or to simply copy another key to easily unlock the lockset. Therefore, the burglarproof lockset has poor protection results as expected. 